Known in the art are player pianos or the like apparatuses. A player piano is an acoustic piano wherein the keys are actuated by a built-in or an externally attached actuator unit including solenoid plungers or the like in accordance with the recorded music playing data such as punched holes on a piano roll and MIDI data on a storage medium, the keys in turn actuating the corresponding piano action hammers to strike the corresponding piano strings, thereby conducting an automatic performance of piano music. An example of such an actuator unit is disclosed in unexamined Japanese patent publication No. H11-184460.
Also known in the art are electronic musical instruments having electronic tone generators wherein the tone generators generate musical tones in accordance with music playing data to conduct an automatic music performance. The music playing data may preferably be of a MIDI format, and may be externally input (e.g. from a sequencer) or may be transferred from an external music work source via a communication network or via a storage medium to a music playing data processing circuit (sometimes further via an internal memory) so that the read-out music playing data control the tone generators to conduct an automatic music performance.
In the case of an electronic musical instrument, an automatic music performance can be conducted without actuating the keys in the keyboard, contrary to the case of an acoustic piano. Recently, however, there is a desire that the keys should move along with the tone generation by the tone generator circuits to visually enjoy the progressing automatic music performance in addition to aural enjoyment of the music. Electronic musical instruments having keys which move along with the progressing automatic music performance conducted by music performance data signals are disclosed, for example, in unexamined Japanese patent publication No. 2001-184054 and in unexamined Japanese patent publication No. 2005-55541.
In the first one of the above referenced publications, the solenoids for actuating the keys are provided near the rear end of the keys at the area away (as viewed from the player) from the swing fulcrum of the keys. In the acoustic piano, the swing fulcrum for the keys resides on the middle rail carrying balance pins according to the regular piano structure, and accordingly a space for placing the solenoid units can be easily prepared in the area away from the middle rail.
In the electronic piano disclosed in the second one of the above referenced publications, a key arm is extended from the key rearward than the swing fulcrum (pivot) of the key, and the rear end of the extended key arm is actuated by the solenoid plunger. This necessitates the space beyond the key and the size of the instrument body will be increased accordingly, and the general merit of an electronic piano as being compact will be impaired.
In the electronic piano disclosed in the third one of the above referenced publications, a swing weight mechanism is provided underneath the key and an actuator (a solenoid plunger) actuates the swing weight mechanism from below. This structure solves the problem of the size increase. However, there is a problem that the actuator and the key bed interfere with each other. In the case of an acoustic piano as in the first one of the above referenced publications, the key bed has a sufficient thickness so that a recess or recesses can be dug therein to accommodate actuators in place of providing through holes or an aperture in the key bed. In the case of an electronic keyboard musical instrument, however, the key bed need not be as thick as an acoustic piano and is usually of a thickness which is insufficient for digging a recess therein, so that an aperture or an opening should be provided in the key bed over an entire width of the keyboard to accommodate the actuators. The key bed is a member which supports the keyboard assembly and bears the player's downward pressing forces of striking the keys to play music, and therefore an aperture or an opening of a length which is almost as long as the entire width of the keyboard may deteriorate the robustness of the key bed, which in turn may deteriorate the robustness of the instrument body.